Improve Diagnostics Webview UI

[rcosta358]

This PR makes some improvements to the UI of diagnostics in the webview:

1. VCs are now displayed in a table layout that include both their binders and predicates
2. The binder type is hidden but shown when hovering the binder
3. Each counterexample assignment is displayed in a single line instead of joined with "&&"
4. The last simplification steps displays "Simplified" instead of the name of the simplification pass